Among the conventionally-known handle structures of walk-behind working machines are ones where a loop-shaped handle is provided on a rear end portion of a handle frame and a main clutch lever is pivotably connected to the handle frame. The loop-shaped handle has left and right raised portions extending upwardly from left and right rear ends of the handle frame, and a cross portion interconnecting respective upper ends of the left and right raised portions (see, for example Japanese Patent Application Laid-Open Publication JP 2004-217116 A). In the handle structure disclosed in JP 2004-217116 A, the main clutch is shiftable to an operating position (ON position) by the main clutch lever being pivotally moved into pressed abutment against the handle. Thus, when the main clutch is in pressed abutment against the handle, a left side portion of the main clutch lever and the left raised portion of the handle, or a right side portion of the main clutch lever and the right raised portion of the handle, can be gripped together by a human operator.
However, the handle structure disclosed in JP 2004-217116 A may impose a great load on the human operator when firmly and reliably gripping the handle together with the main clutch lever. Further, if the human operator is gripping any one of the left and right raised portions when he or she moves or pivots the main clutch lever into pressed abutment against the handle, the main clutch lever would hit a hand of the human operator gripping the raised portion. Thus, when the human operator pivots the main clutch lever into pressed abutment against the handle, he or she has to open the hand, gripping the left or right raised portion, so that the main clutch lever may not hit the hand.